Method to provide precision draw dimension of links

ABSTRACT

A method of punching chain links for a power transmission chain from metal sheet material to ensure precise location of the apertures relative to the outer link contour of the link being created comprising the steps of piercing the metal sheet material to form the apertures and the back contour of the link at a first station. Piercing the metal sheet material to form link flanks at a second station. Shaving the apertures, the link flanks, and the back contour sequentially at a third same station as the metal sheet material is held stationary. Blanking the outer link contour to separate the link from the metal sheet material at fourth station.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention pertains to the field of forming links for a power transmission chain chain. More particularly, the invention pertains to a method of forming links for a power transmission chain that increases the precision and wear resistance of the links produced.

[0003] 2. Description of Related Art

[0004] Power transmission chains are generally comprised of a plurality of link plates, each having a pair of pin holes, arranged in lateral and longitudinal directions, pivotably joined to each other by joining pins inserted into the pin holes. Power transmission chains may be a variety of chain types, for example silent chains or roller chains.

[0005] In order for power transmission chains to work properly and efficiently, the holes or apertures in the links need to be located in a symmetrical position in relation to the link contour. If the apertures of the links are not symmetrical increased noise, vibration, and harshness (NVH) can occur along with an increase in wear of the apertures and the pins.

[0006] Conventionally, the link plates of power transmission chains are made from a progressive die, which is fed through stations by strip progression. In the first station, the apertures of links are pierced. In the second station the link contour is blanked. The piercing of the apertures leaves a rough finish across the profile of the strip consisting of a smooth section where the material sheared (˜30%) and a rough surface where the material tore away (˜70%). The accuracy with which the holes are located relative to the outside link contour is a function of the strip progression and clearance between the strip width and guides built into the die set. Links made by the conventional process result in apertures often being unsymmetrical in relation to the link contour.

SUMMARY OF THE INVENTION

[0007] A method of punching chain links for a power transmission chain from metal sheet material to ensure precise location of the apertures relative to the outer link contour of the link being created comprising the steps of piercing the metal sheet material to form the apertures and the back contour of the link at a first station. Piercing the metal sheet material to form link flanks at a second station. Shaving the apertures, the link flanks, and the back contour sequentially at a third same station as the metal sheet material is held stationary. Blanking the outer link contour to separate the link from the metal sheet material at fourth station.

BRIEF DESCRIPTION OF THE DRAWING

[0008]FIG. 1 shows the layout of steps involved in the progressive punching of chain links using the method of the present invention.

[0009]FIG. 2A shows the noise versus frequency of a chain using links created by a prior art method. FIG. 2B shows the noise versus frequency of a chain using links created by the method of the present invention.

[0010]FIG. 3A shows the chain displacement versus time of a chain using links created by a prior art method. FIG. 3B shows the chain displacement versus time of a chain using links created by the method of the present invention.

[0011]FIG. 4 shows the layout of steps involved in the progressive punching of chain links using an alternate method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0012]FIG. 1 shows the metal sheet material 101 that progresses through predetermined steps (a)-(d), which proceed in the direction shown by the arrow.

[0013] In step (a), the apertures 103, and the back contour 105 are pierced at the same station as the metal sheet material 101 is held stationary. In step (b) the inner link flanks 107 are pierced at a second station. In step (c) the apertures 103, inner link flanks 107 and back contour 105 are shaved sequentially at the same station as the metal sheet material 101 is held stationary. By shaving the apertures, back contour, and link flanks sequentially at the same station, the impact forces delivered by the punches is not all received at one time by the links being produced.

[0014] Shaving is a process whereby an oversized punch is forced through a hole, such that small sliver of material is “shaved” from the existing surface following the contour of the original hole. The purpose of this process is to remove the rough profile and end up with a surface that is 70-90% smooth shear and the remainder rough breakout. Shaving of the apertures, for example, decreases the amount of wear on the connecting pins.

[0015] Shaving may also be applied to the outside surfaces of links to produce outside surfaces that are smooth. Shaving the outside surfaces of the links reduces wear of any plastic surfaces that may contact the chain, for example, chain tensioners or snubbers used to control the chain. Shaving of the outside links decreases the wear on the sprocket where the chain contacts the sprocket.

[0016] By shaving the apertures 103 sequentially with the back of the links 105 and the flanks 107 of the links (equivalent to the links contour 109) at the same station when the metal sheet material 101 is being held stationary, the error in progression of the die set 101 due to the material feeder is eliminated and the symmetrical placement of the apertures 103 in relation to the link contour 109 is much more precise, improving noise performance of the chain as well as reducing sprocket wear. In step (d) the link contour 109 is blanked and the link 110 is completed.

[0017] Improvement of the noise, vibration, and harshness (NVH) for a chain is shown in the graphs of test results in FIGS. 2A and 2B and FIGS. 3A and 3B. FIGS. 2A and 2B compare the noise generated by a chain using the links created by prior art methods and links created by the methods of the present invention respectively, by graphing the sound distribution (noise vs. frequency). As seen in FIG. 2A, the prior art chain has a higher overall noise level than the chain in FIG. 2B. The harmonic peaks are much more distinct in the chain with the links created by the methods of the present invention, showing sound peaks the third through the seventh harmonics between 1000 and 3000 Hz, whereas the prior art chain only shows the peaks at the third through the fifth harmonic, and a higher average level of noise due to meshing between the links of the chain and the sprocket.

[0018]FIGS. 3A and 3B compare the center distance of the chain from a fixed point over time for a chain having links created by prior art methods and a chain having links created by the method of the present invention respectively. As seen in FIG. 3B, the curve is smoother, showing less disorder and displacement of the links of the chain. FIG. 3A, in comparison, shows a rough curve that has a great amount of displacement of the links resulting in increased vibration and harshness.

[0019]FIG. 4 shows another alternative method of providing precision links. As in the previous embodiment, the metal sheet material 101 progresses through predetermined steps, in this case, (a)-(c), in the direction shown by the arrow.

[0020] In step (a), the apertures 103, the back contour 105, and the inner link flanks 107 are all pierced sequentially at the same station as the metal sheet material 101 is held stationery. By piercing the apertures, back contour, and link flanks sequentially at the same station, the impact forces delivered by the punches is not all received at one time by the links being produced.

[0021] In step (b) the apertures 103, the back contour 105, and the inner link flanks 107 are all shaved sequentially at the same station as the metal sheet material 101 is held stationary. By shaving the apertures 103 sequentially with the back of the links 105 and the flanks 107 of the links (equivalent to the links contour 109) at the same station when the metal sheet material 101 is being held stationary, the error in progression of the die set 101 due to the material feeder is eliminated and the symmetrical placement of the apertures 103 in relation to the link contour 109 is much more precise, improving noise performance of the chain as well as reducing sprocket wear. In step (d) the link contour 109 is blanked and the link 110 is completed. In step (c) the link contour 109 is blanked and the link 110 is completed.

[0022] The above embodiments may be performed using a conventional punch press machine as known by one skilled in the art, for example a MINSTER® P245 to a TR260 pulsar.

[0023] The present invention is not limited to the shape of the links shown in FIGS. 1 and 4. It would be obvious to one skilled in the art to adapt or change the die to make links of different shapes.

[0024] Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention. 

1. A method of punching chain links for a power transmission chain from metal sheet material comprising the steps of: a) piercing the metal sheet material to form a pair of apertures, and a back contour of the link at a first station; b) piercing the metal sheet material to form link flanks of the link at a second station; c) shaving the apertures, the link flanks, and the back contour sequentially at a third same station as the metal sheet material is held stationary; and d) blanking an outer link contour to separate the link from the metal sheet material at a fourth station.
 2. The method of claim 1, wherein the power transmission chain is a roller chain.
 3. The method of claim 1, wherein the power transmission chain is a silent chain.
 4. The method of claim 1, wherein the metal sheet is a coil and progresses through steps a) through d).
 5. The method of claim 1, wherein steps a) and b) are combined into one step, such that the metal sheet material is pierced to form the pair of apertures, the back contour, and the links flanks sequentially at one station as the metal sheet material is held stationary.
 6. A method of punching chain links for a power transmission chain from metal sheet material comprising the steps of: a) piercing the metal sheet material to form a pair of apertures, a back contour of the link, and link flanks of the link at a first same station as the metal sheet material is held stationary; b) shaving the apertures, the link flanks, and the back contour sequentially at a second same station as the metal sheet material is held stationary; and c) blanking an outer link contour to separate the link from the metal sheet material at a third station.
 7. The method of claim 6, wherein the power transmission chain is a roller chain.
 8. The method of claim 6, wherein the power transmission chain is a silent chain.
 9. The method of claim 6, wherein the metal sheet is a coil and progresses through steps a) through c).
 10. The plurality of chain links in a power transmission chain created by the method of claim
 1. 11. The plurality of chain links in the power transmission chain created by the method of claim
 6. 12. A machine for creating a plurality of chain links for a power transmission chain from metal sheet material, wherein the machine operates by the steps of: a) piercing the metal sheet material to form a pair of apertures, and a back contour of the link at a first station; b) piercing the metal sheet material to form link flanks of the link at a second station; c) shaving the apertures, the link flanks, and the back contour sequentially at a third same station as the metal sheet material is held stationary; and d) blanking an outer link contour to separate the link from the metal sheet material at a fourth station.
 13. The machine of claim 12, wherein the power transmission chain is a roller chain.
 14. The machine of claim 12, wherein the power transmission chain is a silent chain.
 15. The machine of claim 12, wherein the metal sheet is a coil and progresses through steps a) through d).
 16. The machine of claim 12, wherein steps a) and b) are combined into one step, such that the metal sheet material is pierced to form the pair of apertures, the back contour, and the link flanks sequentially at one station as the metal sheet material is held stationary. 